A Multimedia Broadcast and Multicast Service (MBMS) serves to provide multimedia broadcast and multicast services for users in a radio cell. In a Long Term Evolution (LTE) system, the MBMS can be provided at both an MBMS dedicated frequency layer and a frequency layer which is not shared for MBMS services. The MBMS dedicated frequency layer refers to a frequency layer dedicated to MBMS transmission. A cell configured as an MBMS dedicated frequency layer is referred to as an MBMS dedicated cell, and a cell configured as a frequency layer which is not dedicated to MBMS transmission is referred to as a hybrid MBMS/unicast cell. Unicast and MBMS services in the hybrid MBMS/unicast cell are subject to coordinated transmission in which some instances of time are used for MBMS service transmission and the other instances of time are used for unicast service transmission.
MBMS transmission can be divided into multi-cell transmission and uni-cell transmission. MBMS uni-cell transmission refers to point-to-multipoint (PTM) MBMS transmission only in the coverage area of a specified cell and supports no combination of MBMS transmission from a plurality of cells; and MBMS multi-cell transmission has to support transmission over a Multicast Broadcast Single Frequency Network (MBSFN), that is, consistent signals are transmitted concurrently in a plurality of cells.
MBMS related logical channels include a Multicast Traffic Channel (MTCH) and MBMS point-to-multipoint Control Channel (MCCH), where:
The MTCH is a point-to-multipoint downlink channel on which MBMS traffic data is transmitted from a network to a User Equipment (UE), and this channel is available only to a UE capable of receiving MBMS services. Information of the MTCH is indicated by its corresponding MCCH. The MCCH is indicated to the UE on a Broadcast Control Channel (BCCH) and further the MTCH is indicated to the UE on the MCCH from the network so that the UE receives MBMS services carried on the MTCH.
The MCCH is a point-to-multipoint downlink channel on which MBMS control information is transmitted from a network to a UE, and one MCCH controls one or more MTCHs. The MCCH can be read only by a UE receiving MBMS services. The MCCH is mapped onto an MCH in the case of MBSFN transmission and onto a Downlink Supplementary Channel (DL-SCH) in the case of non-MBSFN transmission.
Radio Network Temporary Identifiers (RNTIs) in the existing system are divided into two categories: one category is cell-specific RNTIs, e.g., a Paging RNTI (P-RNTI), a System Information RNTI (SI-RNTI), etc., and Downlink Control Information (DCI) or common signaling corresponding to common information to be read by all the users in a cell is scrambled with this category of RNTIs and then transmitted in a common search space of a Physical Downlink Control Channel (PDCCH); and the other category is user-specific RNTIs, e.g., a cell RNTI (C-RNTI), etc., i.e., a serial number of each UE at the MAC layer, and control information or dedicated signaling corresponding to user-specific data information is scrambled with this category of RNTIs and then transmitted in a user-specific search space of the PDCCH. Upon reception of the control information, a user can know whether the control information is intended for the user simply by detecting the RNTI used for scrambling.
Upon reception of the PDCCH, the user can not be aware of a specific format in which a base station transmits the downlink control information and therefore has to perform blind detection of the DCI format, that is, the user has to decode the signaling respectively with different lengths of information and levels of CCE aggregation defined in the system and determine from a CRC check whether the signaling is received correctly.
The inventors have identified during making of the invention the following technical problem present in the prior art;
The MTCH related control information is transmitted periodically on the MCCH, and the contents of the control information carried on the MCCH are configured quasi-statically and less variable. The UE listens periodically to the MCCH, and the same contents of the control information received on the MCCH may be duplicated, thereby resulting in a resource waste.